Life Science ( Heredity )?

Question

1. Hairline shape is an inherited trait in humans. The window's peak alleles is dominant and straight hairline allele is recessive. Predict how both parents with window's peaks could have a child without a window's peak hairline .

2. One fruit fly is heterozygous for long wings, and another fruit fly is homozygous for short wings. Long wings are dominant to short wings. Using a punnet square, find out what percent of the offspring are expected to have short wings .

Answer 1

1. Both parents carry both a dominant and a recessive gene (heterozygous).  Therefore they have a 25% chance of having a child without a widow's peak.

2. 50% chance that they will have a short winged baby fly.

Answer 2

For 1. Assuming window's peak (W)is dominant, and straight hairline is recessive(S), the parent may either have WW or WS.

The only way the child can have straight hairline is when they get both the SS. So the chance of it happening is 25%

WW x WW = WW (windows peak)

WS x WW = WS/WW (windows peak)

WW x WS = WW/WS (windows peak)

WS x WS = SS (straight hairline)

As you can see, the chances of the child getting straight hairline is 1 out of 4 so that means a 25% chance.

With the 2nd qn, assume Long wings are LL, heterozygous long wings are LS and short wings are SS,



The first parent would be LS and the second would be SS.

So,

LS x SS = LS or

LS x SS = SS

So the chances of the baby fruit fly getting short wings is 50%.

I hope i got my maths correct. =x